Solar cells are electrical devices for direct generation of electrical current from sunlight. A plurality of solar cells can be connected by respective interconnect structures to form a solar cell module. A plurality of modules can be connected to form an array.
Some solar cell devices include a protective cover over the solar cells. Light passes through the protective cover to the solar cells below for conversion into electrical current via the photovoltaic effect. Optical transmittance through the protective cover affects the efficiency of a solar cell device. For example, the amount of power produced by a solar cell depends on the amount of light that passes through the protective cover and reaches the absorber layer of the solar cell. Additionally, the traveling length of the transmitted light determines the distance it will travel through the absorber layer.
Optical loss through the cover due to reflection, refraction and absorption reduces the amount of light that reaches the solar cell and, in particular, the absorber layer. For example, reflectance at the air/glass interface for a glass protective cover is around 4-5% for normal incidence. Optical loss through the protective cover consequently reduces the efficiency of the solar device.